code: def _ndtr(x):
      """Implements ndtr core logic."""
      half_sqrt_2 = tf.constant(
          0.5 * np.sqrt(2.0), dtype=x.dtype, name="half_sqrt_2"
      )
      half = tf.constant(0.5, x.dtype)
      one = tf.constant(1.0, x.dtype)
      two = tf.constant(2.0, x.dtype)
      w = x * half_sqrt_2
      z = tf.abs(w)
      y = tf.where(
          z < half_sqrt_2,
          one + tf.math.erf(w),
          tf.where(w > 0.0, two - tf.math.erfc(z), tf.math.erfc(z)),
      )
      return half * y
  
file_path: probability/tensorflow_probability/python/internal/special_math.py
imports: import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.internal import dtype_util
label_desc: Use image node_id 2 for calling a global function with example usage: _ndtr(x) and returns: unknown